Schottky junctions are used for fast switching power devices due to their low losses and high switching speed. The barrier height of a Schottky junction depends on the semiconductor material and the metal used to form the Schottky junction with the semiconductor material. In addition to that, surface defects and other surface characteristics influence the quality of the Schottky junctions and may shift the barrier height. However, well defined Schottky junctions are needed, particularly for power devices.
To reduce the variation of the Schottky barrier height, the surface of the semiconductor substrate is commonly subjected to a dry-chemical RIE process (reactive ion etching) to saturate the surface with fluorine which is referred to as fluorine covering. However, the fluorine covering is only suitable in combination with a subsequent vapour deposition of a Schottky barrier forming metal. Furthermore, the fluorine covering does not appear to be stable enough.
In view of the above, there is a need for improvement.